It is well-known that most semi-conductor devices suffer from infant mortality, resulting in billions of warranty losses due to early field failures. Burn-in is an important engineering procedure used to identify defective units by subjecting all units to a screening test with a certain duration. Optimal determination of the burn-in settings is of particular importance, as it enhances field performance of a product and saves field operation costs up to the hilt. Motivated by some practical problems with complex failure processes, this thesis is aimed at developing some practical burn-in models to help determine the optimal burn-in settings.
We first propose a burn-in scheme based on change points of the p-percentile function of the residual life function. This scheme is able to simultaneously yield the optimal burn-in duration and the optimal warranty period, which is important for products whose warranty coverage is yet to be determined. We also identify severe infant mortality faced by products sold with two-dimensional warranties, and subsequently propose two novel burn-in models. In view of the fact that modern manufacturing technique has led to what is commonly known as highly reliable products, this thesis advocates degradation-based burn-in approaches that base the screening decision on a product?s degradation level after burn-in. We first develop two degradation-based joint burn-in and preventive maintenance models for products whose degradation is measurable. Then, we recognize the fact that product failures are much more complex, and thus propose a degradation-based burn-in framework under competing risks. In addition, we propose a bi-objective burn-in framework that simultaneously takes the cost and field performance of a burnt-in unit into consideration. These proposed models are successfully applied to solve a number of real problems, which shows the significant practical contributions of this thesis.